fine grading for pavement
Achieving finish grades is typically made possible by finish grade stakes placed by the surveyor. On the stake will be a cut or fill notation and an indicator showing where the final grade should be, allowing the contractor to subtract the depth of the pavement material to acquire top of aggregate base elevation. The amount and location of the stakes required is typically a function the installing contractors preference as to what helps him complete the work most efficiently and accurately. Perimeter stakes are typically sufficient for smaller areas. Larger areas with lots of slopes, drainage structures, and high/low points will require intermediary ‘temporary’ stakes.
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A more modern day form of layout involves the use of GPS software which actually indicates to the grader/dozer operator, what the elevation and angle of the blade on the machine needs to be for proper design pavement elevation.
A pavement aggregate base is most commonly ‘roughed’ in with a dozer. In theory, pavement bases more than 6″ in thickness should be compacted in more than one lift, as roller compaction efforts are really only effective to a 4-6″ depth depending on the machine size, weight, and vibratory capability.
Once a pavement base material is rough placed, the next step is to fine grade the top inch or two to set the stage for the finish pavement grades to be brought to correct elevations. Ideally the rough aggregate base will be brought to +/- 1″. The scope of the fine grading work will be to either cut or fill the material to match as close as possible to the finish pavement elevations, less the thickness of the proposed pavements. Finish grading work is most commonly done with a grader and a roller following behind.
Finish grading is typically separated from rough grading and mass aggregate placement for several different reasons. One reason is that it is sometimes performed by two separate companies. One contractor will install the rough aggregate base, and the contractor installing the pavement will complete the aggregate base work by fine grading prior to his pavement. This allows more control for the paving contractor, and also helps alleviate any disagreements about the final base elevations being completed at incorrect grades and affecting pavement thickness.
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For smaller hard to reach areas and minor trimming/filling, it can also be useful to have a small track or rubber tired skidsteer on site. Stone box attachments and GPS are handy add-ons for skidsteer loaders.
